Media Compression Skill

Video Compression

# Compress with default settings (good balance)
python scripts/compress_video.py video.mp4 --output video_small.mp4

# Resize to 720p
python scripts/compress_video.py video.mp4 --height 720

# Target specific file size (approximate)
python scripts/compress_video.py video.mp4 --target-size 50mb

# Lower quality for smaller file
python scripts/compress_video.py video.mp4 --crf 28

# Batch process all videos in folder
python scripts/compress_video.py ./videos --output ./compressed --height 480

# Preview mode - see what will happen without compressing
python scripts/compress_video.py video.mp4 --height 720 --preview

# Keep backup of original file
python scripts/compress_video.py video.mp4 --height 720 --backup

Common Use Cases

1. Upload to Website (Image)

Most websites need images under 500KB:

python scripts/compress_image.py photo.jpg --max-size 500kb --format webp

2. Email Attachment (Image)

Email often has 25MB limit:

python scripts/compress_image.py scan.pdf.jpg --max-size 5mb --quality 90

3. Social Media Video

Platforms prefer 720p, smaller files:

python scripts/compress_video.py clip.mov --height 720 --crf 23 --preset fast

4. Archive Old Videos

Maximum compression for storage:

python scripts/compress_video.py old_video.avi --crf 28 --preset slow --height 480

5. Convert Format Only

Keep quality, just change format:

# Image
python scripts/compress_image.py image.png --format jpg --quality 95

# Video
python scripts/compress_video.py video.mov --output video.mp4 --crf 18

Parameters Reference

Image (compress_image.py)

Video (compress_video.py)

Quality Guidelines

Images

• 90-95: High quality, minimal compression artifacts
• 85: Sweet spot (default) - good quality, significant size reduction
• 70-80: Acceptable for web, smaller files
• 50-60: Low quality, visible artifacts

Videos (CRF)

• 17-18: Visually lossless, archival quality
• 20-22: High quality, professional use
• 23: Default, good balance (recommended)
• 28: Smaller files, acceptable quality
• 35+: Low quality, preview/draft only

Presets

• ultrafast: Fastest encoding, largest files
• fast: Quick results, slightly larger
• medium: Default balance
• slow: Better compression, smaller files
• veryslow: Maximum compression, smallest files

Batch Processing

When input is a directory:

• All supported files are processed
• Output directory structure mirrors input
• Progress shown for each file
• Original and compressed sizes displayed

Example:

$ python scripts/compress_image.py ./vacation_photos --output ./compressed --max-size 500kb
找到 24 个图像文件
[1/24] 处理: IMG_001.jpg
  ✓ 2847.3KB → 456.2KB (84.0% 减少)
[2/24] 处理: IMG_002.png
  ✓ 1532.1KB → 298.5KB (80.5% 减少)
...

Troubleshooting

"ffmpeg not found"

Install ffmpeg first:

# Ubuntu/Debian
sudo apt update && sudo apt install ffmpeg

# macOS
brew install ffmpeg

"Permission denied"

Make scripts executable:

chmod +x scripts/*.py

Quality too low

Increase quality setting:

# Image
python scripts/compress_image.py photo.jpg --quality 90

# Video
python scripts/compress_video.py video.mp4 --crf 20

File not smaller

• Try lower quality or smaller dimensions
• Some files are already optimally compressed
• Use --max-size to force target size

Batch processing stops

Check that all files in directory are valid images/videos. Corrupt files may cause errors.

Advanced Tips

1. Strip metadata for privacy (default behavior)
2. Use WebP for best web compression
3. 720p height is usually enough for mobile viewing
4. CRF 23 + preset slow gives great results for archiving
5. Test with one file before batch processing

References

• FFmpeg Guide - Detailed ffmpeg commands and parameters